1. Field of the Invention
This invention relates to an ATM exchange, and more particularly to a method of and a system for exchanging a low speed ATM channel of 3 Mb/s or less.
2. Description of the Related Art
The minimum basic unit in exchanging by an ATM exchange is an ATM cell formed of 53 bytes. The ATM cell has an information field called payload including 48 bytes, and such 48 bytes are handled as 1 block in exchanging. Accordingly, in a synchronous transmission line in which 1 frame requires 125 .mu.S, exchanging by an ATM exchange yields an information absent field in an ATM cell, resulting in drop of the transmission efficiency. Consequently, exchanging by an ATM exchange is not suitable for ATM communication of approximately 3 Mb/s (48 bytes/125 .mu.S) or less.
Low speed synchronous information such as voice is not suitable for exchanging by an ATM exchange because the minimum unit of composition of an ATM is one cell and information of the payload field is not divided.